C0105

Code

Generic C — Chassis

ABS Wheel Speed Sensor Circuit Fault

Brand: Generic

Type: C — Chassis

Views: UK: 4 EN: 8 RU: 4

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ABS warning lamp illuminated
Traction control / ESC lamp may also illuminate
ABS may not function during hard braking (loss of anti-lock feature)
Intermittent or unexpected ABS activation
Erratic wheel speed readouts on a scan tool; possible speedometer/cruise anomalies on some vehicles

Use a scan tool to read stored codes, freeze frame and live wheel speed data
Visually inspect sensor, connector and wiring at wheel for damage, corrosion or contamination
Inspect reluctor (tone) ring for missing/bent teeth, heavy rust or debris and correct seating
Check for proper sensor mounting and air gap per vehicle spec
Perform a wiggle test on harness while watching live data for intermittent changes
Check ABS fuses and module connectors for corrosion or poor contact

Passive (VR) sensor: DC resistance typically in the hundreds to a few thousand ohms (varies by vehicle). Produces AC voltage proportional to wheel speed (hundreds of mV at low speed up to several volts AC at higher speed). Frequency increases with speed.
Active (hall/VR with electronics) sensor: produces a digital square wave (typically 0–5V or 0–12V) or a PWM-type signal. Reference supply often 5V or 12V. Frequency proportional to wheel speed.
Fault signatures: open circuit → infinite resistance/zero signal; short to ground/battery → near 0V or constant voltage; intermittent → fluctuating or dropouts in live data.

Connect an OBD-II / ABS-capable scan tool, read codes and note freeze frame and live wheel speed values. Attempt to reproduce fault while monitoring live data.
Visually inspect the suspect sensor, connector and wiring harness for damage, corrosion, pulled pins, or water ingress. Repair or clean as needed.
Inspect the reluctor (tone) ring/ABS ring and hub/bearing for missing teeth, heavy rust, deformation or excessive play. Replace or repair if damaged.
With wheel off the ground and supported safely, measure sensor electrical parameters: for passive sensors measure resistance (compare to spec) and AC voltage while spinning wheel; for active sensors check reference voltage, output square wave (0–5/12V) and ground. Use oscilloscope if available to confirm waveform.
Perform continuity and short-to-ground/battery checks on sensor wiring back to the ABS module connector (pin-to-pin). Repair any broken wires or shorts.
Reconnect and perform a wiggle test across suspension travel and steering lock while watching live data to find intermittent faults.
After repairs, clear codes, perform a road test and re-scan to ensure code does not return. If sensor and harness test good but problem persists, consider ABS module or internal connector faults and refer to manufacturer module diagnostics.
Safety note: support the vehicle safely on lift or jack stands before spinning wheels; follow manufacturer torque and service procedures.

Corroded/loose sensor connector or damaged wiring harness
Failed wheel speed sensor (water ingress or internal failure)
Damaged or missing reluctor ring tooth or excessive debris on reluctor
Intermittent wiring short/open due to chafing at suspension/steering articulation
Fault in ABS control module (diagnose after wiring and sensor verified)